For some objects requiring temperature control, the total amount (cumulative value) of heat received by the objects with time is important in addition to temperature change for every time and temperature information at a certain moment. Examples of such objects include equipment and food.
For example, some equipment may cause trouble such as degradation and malfunction if it is heated to a certain temperature or higher. Further, some food must not be exposed to a predetermined temperature for a certain period of time or more for keeping quality, while some food needs to be exposed to a predetermined temperature for a certain period of time or more for safety and hygiene. Furthermore, also in the reconstitution (reconstitution with hot water) of instant cup noodles and the like, the total amount (cumulative value) of heat received with time is important.
Thus, several proposals have been made for a temperature-indicating label for checking the total amount (cumulative value) of heat received with time (refer to Patent Literature 1).